Gases (H)
Page 1: Gases vs. Liquids and Solids
Gases differ from liquids and solids in several ways:
Gases have no fixed shape or volume.
They expand to fill the volume of their container.
The volume of a gas is not constant, but varies with pressure and temperature.
To measure or predict gaseous products of reactions, one must use the Ideal Gas Law and other gas laws.
Page 2: Chemical Equations
Write balanced chemical equations for the following reactions:
Carbonic acid + Aluminum Hydroxide: [ H_2CO_3 + 2 Al(OH)_3 \rightarrow 2 H_2O + Al_2(CO_3)_3 ].
Hydrofluoric Acid + Sodium Carbonate: [ 2 HF + Na_2CO_3 \rightarrow 2 NaF + H_2O + CO_2(g) ].
Page 3: Atmospheric Pressure
Atmospheric pressure is the force exerted by the weight of air above a surface, varying with altitude.
Page 4: Breathing Mechanics
To take a breath, the diaphragm contracts, enlarging the thoracic cavity.
This creates a negative pressure that draws air into the lungs.
Page 5: Water Movement in a Straw
When drinking through a straw, a reduction of pressure occurs inside the straw, causing the external pressure to push water up.
Page 6: Juice Box Collapse
A juice box gets crushed as it is being drank because the internal pressure decreases when fluid is removed, and atmospheric pressure crushes it.
Page 7: Snorkeling Depth
One cannot snorkel 10 feet underwater because at that depth, the pressure exceeds the breathing capacity without specialized equipment.
Page 8: Suction Cups
A suction cup sticks to a wall by creating a vacuum that prevents air from entering.
To remove it, lift the edge to break the seal, allowing air to enter.
Page 9: Water Stability in a Tube
Water does not fall out of a tube due to cohesive forces and air pressure preventing outflow.
Page 10: Barometers
Barometric pressure can be measured using a barometer, where 33 feet of water or 760 mm Hg equates to 1 atmosphere (atm).
Page 11: Balloon Behavior
Molecules in a balloon are in constant motion.
Balloon size is affected by temperature, pressure, and the number of gas molecules it contains.
Page 12: Gas Properties
The volume of a gas is not defined without pressure and temperature information.
Units of measurement include:
Volume: m³, cm³, mL, liters
Pressure: atm, mm Hg, Pascals
Temperature: Kelvin (K)
Page 13: Kinetic Molecular Theory
The energy of gas is signified by the motion of its molecules.
Kinetic energy (KE) is proportional to temperature.
Lighter molecules move faster at the same temperature than heavier ones.
Page 14: Volume Determinants for Balloons
Three factors that determine balloon volume:
Pressure
Temperature
Amount of gas (moles)
Page 15: Comparing Balloons
Both balloons have the same temperature and pressure, but will differ in behavior due to atomic mass (lighter He will expand faster).
Page 16: Gas Laws
Key gas laws include:
Boyle’s Law: P1V1 = P2V2 (constant temperature)
Charles’ Law: V1/T1 = V2/T2 (constant pressure)
Gay-Lussac’s Law: P1/T1 = P2/T2 (fixed volume)
At STP: 760 mm Hg and 273 K.
Page 17: Gas Law Applications
Determine the gas law relevant to specific scenarios:
Helium balloon deflation involves Boyle’s Law.
Aerosol can explosion relates to combinations of gas laws and KMT principles regarding temperature increase.
Helium balloon rising involves Boyle's and Charles's laws; gas expands with decreasing pressure.
Page 18: Balloons Ranked by Size
Rank these gases from smallest to largest volume under standard conditions:
H2 < He < Ar < Cl2
Page 19: Volume Change Calculation
To find temperature needed to expand a 3 L balloon to 4 L, apply Charles's Law.
Helium atoms diffuse faster than carbon dioxide molecules due to smaller mass.
Page 20: Avogadro's Principle
Volume of a gas is directly proportional to the number of moles (Volume ∝ n), but not dependent on the type of gas.
Page 21: Pressure Equilibrium
Understanding partial pressures in a gas mixture based on atmospheric pressure equations.
Page 22: Partial Pressure Calculations
Total gas pressure inside a balloon can be found using Dalton's Law of Partial Pressures.
For example: if 40% is O2, calculate the partial pressure accordingly.
Page 23: Ideal Gas Law
The Ideal Gas Law is expressed by: PV = nRT.
R = 0.0821 L.atm/(K.mol)
Use it to find unknown volume, moles, pressure, or temperature.
Page 24: Ideal Gas Calculations
Sample problems:
Volume of 0.25 moles of Helium at 12°C and 740 mm Hg equals 6.0 L.
Mass of 244 mL of Hydrogen gas at STP equates to 0.022g.
Page 25: Water Displacement Errors
Adjustments for collecting gases by water displacement:
Equalize water levels before recording gas volume.
Calculate true gas pressure considering atmospheric pressure.
Page 26: Water Vapor Pressure Adjustment
When collecting gas, account for water vapor pressure to find accurate molar calculations.
Example provided for calculation adjustment.
Page 27: Butane Lab Procedures
Steps to collect gas, measure volume, and account for atmospheric pressure and water vapor pressure when conducting gas experiments.
Page 28: Standard Molar Volume
At STP, 1 mole of gas occupies 22.4 L.
Example: calculate volume of NO2 produced from the reaction of O2 to determine yield under specific conditions.
Page 29: Molar Volume Calculations
Example calculations for volume of NH3 gas based on given mass, temperature, and pressure conditions.
Page 30: Molecular Weight Calculation
Determine the molecular weight of an unknown gas from sample measurements using the Ideal Gas Law.
Page 31: Chemical Reactions Involving Phosphorus
Writing balanced equations for reactions and estimating theoretical yields and percent yield of products.
Page 32: Laboratory Reactions with Oxygen
Analyze the limiting reactant and yield calculations for phosphorus and oxygen reactions with diphosphorus pentoxide production.
Page 33: Reaction of Calcium Carbonate
Write balanced equations for calcium carbonate and hydrochloric acid reactions.
Calculate pressure of CO2 produced in the reaction.
Page 34: Reaction of HCl with Sodium Carbonate
Balanced equations for the reaction resulting in the production of CO2 gas, along with yield calculations.
Page 35: Density Calculations of Gas
Calculate the density of CO gas given its volume, pressure, and temperature conditions.